Invertebrates: Egg Identification

A single dot, a squiggle of white, a floating orange ball – eggs come in all shapes, sizes, and colors! Of course, the easiest way to tell what it could grow up to be is to find mom nearby, but that’s not always possible. These are just a few of the most common eggs found in an aquarium.

Cerith Snail Eggs (Cerithium sp.)- Reef Safe:

Cerith snails are a beneficial part of a reef tank clean-up crew. They reproduce in captivity to some extent (some aquarists have more success than others, and the juveniles make it to adulthood in small numbers). The egg pattern is very distinctive, as shown below with the mother (and possibly father). The egg pattern will vary by species, but most have something similar to this white swerving pattern. More info on snails

Cerith Snail with Eggs

Stomatella Snails (Stomatella sp.)- Reef Safe:

Stomatella snails are hands-down my favorite snail. They come in nearly all colors (like the black one below, but also in red, silver, green, etc.) They frequently enter an aquarium as a hitchhiker, scour the tank for algae, and then reproduce prolifically. They’re broadcast spawners, so they reproduce by climbing high in the aquarium and releasing small puffs of sperm and eggs which look like smoke. More info on snails

Stomatella Snail

Although the stomatella snail can’t be seen in the photo below, there is one hiding under the Scolymia coral releasing either sperm or eggs (white smoke-looking mass to the left of the Scolymia). This event lasted about 3 minutes. Unfortunately, I’ve had a hard time determining their life cycle times since they *constantly* have new batches of babies.

Stomatella Spawning

Nerite Snail Eggs (Nerita sp.) – Reef Safe:

Nerite snails are also a great snail, but I only know of one person who had nerite eggs hatch and grow successfully to adults (in other words, most eggs do not become adults…or even make it to juveniles.) The eggs look like white sesame seeds and are sometimes found singularly or in small groups (like the four in the photo below). More info on snails

Nerite Snail with Eggs

Developing Nerite Eggs

Conch (Strombus sp.) – Reef Safe:

I had (what I assume to be) a mated pair of fighting conchs that regularly laid eggs. Unfortunately, I never had success raising these in captivity. More info on snails

Ok, so maybe the taxonomy isn’t entirely straightened out on this snail yet, but regardless of name, they’re great snails. As you can see by the egg sacs below, they reproduce faster than rabbits. If you’re sick of buying snails, then these are your best choice in my opinion. They graze over rocks and on glass, stay small, and their population waxes and wanes with food supply. You can find more information on breeding and raising these here.

Collumbellid Snail

Collumbellid Snail Eggs

Week Old Collumbellid Juvenile Snail

Polyclad Flatworm – Not Reef Safe:

These massive flatworms are not reef safe due to their predatory behavior. I found one of these flatworms inside a hole in the live rock attached to a coral along with the eggs shown below. Although I am not 100% certain the eggs are from the flatworm, there were no other large invertebrates within the live rock. Additionally, the eggs resembled very large Acropora-eating Flatworm (AEFW) eggs, another polyclad flatworm species. More info on flatworms here.

Polyclad Flatworm

Polyclad Flatworm Eggs

Acropora-eating Flatworms (Amakusaplana acroporae) – Not Reef Safe:

As the common name implies, these flatworms only eat Acropora corals. Although they usually lay their eggs directly on the Acropora corals, the eggs can sometimes be found near Acropora corals, like on a frag plug in the photo below.

Acropora-eating Flatworm

Acropora-eating Flatworm Eggs

Gall Crab Eggs – Reef Safe with Caution:

There is quite a bit of debate over whether gall crabs are reef safe, but I, personally, have not experienced any issues. The female builds a small hole in live rock, and corals grow around the crab. Since sick corals often contain gall crab inhabitants, the crabs are often blamed for the coral’s ill health. I should note that extremely large, healthy corals in the wild house gall crabs with no noticeable problems. The female below is carrying eggs (in yellow).

Gall Crab with Eggs

Coral Eggs – Reef Safe:

Coral eggs, like the Tubastrea coral eggs shown below, are typically orange balls. The coral below actually started spawning while in a coral dip!

Tubastrea Eggs

Tubastrea Eggs

Unknown Eggs – Varies:

I have no idea what these were (and most were hatched). Although not every egg is covered here that you might find, hopefully this gives you a good start!

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Disclaimer

Although I try my best to keep this page up-to-date with the latest and greatest information, I cannot assume any responsibility/liability. Marine biology information changes constantly, each captive marine environment is different, and there are many variables at play. What works for one person may not work for another. If you find any errors or outdated information, please contact me!